A vast number of commercial products that are difficult to produce synthetically are today produced by fermenting organisms. Such products include alcohols (e.g., butanol, ethanol, methanol, 1,3-propanediol); organic acids (e.g., acetic acid, citric acid, gluconate, gluconic acid, itaconic acid, lactic acid, succinic acid, 2,5-diketo-D-gluconic acid); ketones (e.g., acetone); amino acids (e.g., glutamic acid); gases (e.g., H2 and CO2), and more complex compounds, including, for example, antibiotics (e.g., penicillin and tetracycline); enzymes; vitamins (e.g., riboflavin, B12, beta-carotene); and hormones. Fermentation is also commonly used in the consumable alcohol (e.g., beer and wine), dairy (e.g., in the production of yogurt and cheese), leather, and tobacco industries. A vast number of processes of producing fermentation products, such as ethanol, by fermentation of sugars provided by degradation of starch-containing materials are known in the art. However, production of fermentation products, such as ethanol, from such starch-containing material is still too costly. Therefore, there is a need for providing processes that can increase the yield of the fermentation product and thereby reduce the production costs. It is an object of the present invention to provide improved processes for producing fermentation products.